This invention relates to combine harvesters and in particular to such harvesters (hereinafter referred to as being of the kind described) which have twin axial separating rotors and a transverse feed beater under which a crop stream is conveyed before entering rotor housings for processing by the rotors, flights being provided on the feed beater which tend to move the crop passing under the beater axially outwardly from a central zone of the beater into the two rotors.
There are two main types of separating apparatus used within combine harvesters to separate grain from the straw with which it grows. In traditional combines used mainly in Europe, the threshed crop material is separated by means of a plurality of longitudinally-extending straw walkers which oscillate so as to ‘walk’ the straw to the rear of the combine whilst allowing the grain to drop through sieves formed in the base thereof. This technology is well established and has been acceptable for many decades.
More recently, with the increase in throughput demands on the combine, straw walkers have been replaced with longitudinally-extending separating rotors which each rotate around a longitudinal axis. In this arrangement, often referred to as ‘axial’, the crop stream is fed into the forward end of the separating rotor (or rotors) and is conveyed around the rotors within housing units in a rearwardly extending corkscrew path. Under the same basic principal as for the straw walkers, the straw is conveyed to the rear of the combine and the separated grain falls through holes in the rotor housing.
Axial combines have been employed in the United States, for example, for many years where the typical crop yield per unit area is significantly lower than that in Europe. In this case, however, the axial rotors also serve to thresh the grain from the straw. In European applications where the crop yield is more substantial, and typically of a greater moisture content, a transverse threshing drum often precedes the separating rotors, thereby giving an arrangement which is commonly known as ‘hybrid’ separation.
So as to maximise throughput of a hybrid combine, twin axial separating rotors, which extend side by side within respective housings, are adopted. It is well recognised that the mechanism by which the crop flow is conveyed from the transverse threshing drum to the twin rotor housings is a significant factor on the power consumption of the machine. As a result there is much effort to improve the transfer of the crop into the separating rotors.
In order to split a single crop stream presented to the separating rotors, a preceding feed beater which rotates on a transverse axis is known to comprise directional vanes which direct the crop flow away from a central zone of the beater and toward respective crop streams associated with the two rotors. However, it has been found that the directional vanes of the feed beater lead to increased back-feeding of the crop stream around a central part of the feed beater. This problem is particularly apparent for bulky and/or moisture-laden crops. Once wrapped around the feed beater, the effectiveness of the directional vanes decreases to an extent where further crop material accumulates around the central part, eventually leading to jamming of the entire threshing apparatus. Once jammed, the operator must undergo the time-consuming task of manually dislodging the wrapped material.